How do I change the hostname without rebooting?

Question

Is it possible to change the hostname of my Raspberry Pi permanently, but also have the change take effect without rebooting?

Answer 1

Yes, it is possible using the following steps. Replace "mynewhostname" with whatever hostname you are changing to.

1) First change the hostname read on bootup, to make the change permanent.

echo "mynewhostname" | sudo tee /etc/hostname

2) Edit the hosts-file so that the new name can be resolved.

Replace the line 127.0.1.1 raspberrypi (raspberrypi being the old hostname) with 127.0.1.1 mynewhostname.

sudo nano /etc/hosts

3) Change the currently used hostname.

This is the trick to skip rebooting, issue the following command to change the currently used hostname:

sudo hostnamectl set-hostname "mynewhostname"

4) Restart the mDNS daemon

To be able to use mynewhostname.local from other machines, we need to restart the mDNS daemon to respond to the new hostname.

sudo systemctl restart avahi-daemon

Answer 2

Here is a repeat of Linus's reply into a shell script (with non-manual change of /etc/hosts).

setHostName:

host_name=$1
echo $host_name | tee /etc/hostname
sed -i -E 's/^127.0.1.1.*/127.0.1.1\t'"$host_name"'/' /etc/hosts
hostnamectl set-hostname $host_name
systemctl restart avahi-daemon

Usage:

./setHostName NEW_NAME

Answer 3

Added a few sudo in and a re-login to get the prompt updated assuming the user is pi

change host name

    host_name='AtHome'
    echo $host_name | sudo tee /etc/hostname
    sudo sed -i -E 's/^127.0.1.1.*/127.0.1.1\t'"$host_name"'/' /etc/hosts
    sudo hostnamectl set-hostname $host_name
    sudo systemctl restart avahi-daemon
    sudo su -l pi

Answer 4

To follow on from Linus's answer...

In /etc/hosts, the line 127.0.0.1 is for localhost (the loopback interface lo) and should not be changed.

The line that should actually be changed is 127.0.1.1 (as both p8me's answer and Paul's answer illustrate).

From What is difference between localhost address 127.0.0.1 and 127.0.1.1:

The reason it's used as the IP for your hostname is explained in Section 10.4 of the Debian Reference Manual.

Quote:

Some software (e.g., GNOME) expects the system hostname to be resolvable to an IP address with a canonical fully qualified domain name. This is really improper because system hostnames and domain names are two very different things; but there you have it. In order to support that software, it is necessary to ensure that the system hostname can be resolved. Most often this is done by putting a line in /etc/hosts containing some IP address and the system hostname. If your system has a permanent IP address then use that; otherwise use the address 127.0.1.1.

Answer 5

[SOLVED]

Building upon MichielB's answer here, the code for changing it dynamically through a new_hostname file after the pi has been set up is here, no modification to the command line is necessary and you will have NOT have to reboot the pi after its done. This code is for the situation where you wanna mass produce an OS image from a base image and your greater shell script modifies the hostname file to create its own unique OS image, thus the whole hostname changing process is automated and no reboot is necessary. The code can be used with custom front-end services to change the hostname dynamically

More details in the github link: https://github.com/techscapades/change-raspberrypi-hostname-from-file-no-reboot

#!/bin/bash

set +e

CURRENT_HOSTNAME=`cat /etc/hostname | tr -d " \t\n\r"`
NEW_HOSTNAME=`cat /path_to_new_hostname_file | tr -d " \t\n\r"`

echo `cat /path_to_new_hostname_file | tr -d "\t\n\r"` >/etc/hostname
sed -i "s/127.0.1.1.*$CURRENT_HOSTNAME/127.0.1.1\t$NEW_HOSTNAME/g" /etc/hosts
echo `cat /etc/new_hostname | tr -d "\t\n\r"` >/proc/sys/kernel/hostname

exit 0

you can throw in systemctl restart avahi-daemon before it exits but you might have to wait a while before you can access your_new_hostname.local again